The invention relates to a nozzle pin used in co-injection apparatuses and methods. A co-injection apparatus injects two different materials, typically an inner-core material and an outer-skin material, into a mold cavity.
A co-injection manifold receives material, usually plastic, from two different injection units and combines the two materials into a single stream that flows into a mold or die. The co-injection manifold, and the co-injection nozzle housed therein, are located between injection units and the single or multi-cavity mold cavity. A typical co-injection manifold is fixed to the injection units or is located within the mold itself.
In order to produce end-products having high structural integrity, it is desirable that a uniform, even flow of each material be distributed into the mold cavity. In other co-injection methods and apparatuses, nozzle pins have been employed to facilitate the even flow of the materials, and more particularly the outer skin material. But often knit or weld lines (i.e. lines of intersection between materials) develop when using these conventional apparatuses and methods, thereby resulting in non-uniform distribution of the materials and ultimately, structural problems in the end-products. Knit lines also produce color streaking in end-products. As a result, co-injection methods and apparatuses that eliminate knit lines and uneven flow of co-injection materials are desirable.